desertification Flashcards
what is an arid region ?
an arid region is a region which experiences less than 250mm of rainfall per year
what is a semi arid region
a semi arid region is a place which experiences between 250 - 500 mm rainfall a year
why are deserts hot ?
deserts sit in low/mid latitude regions where there is high insolation. the sun is at a high angle of incidence allowing steep concentrated rays of solar radiation baking the surface of the desert
what is the definition of an exogenous water source
exogenous water sources originate from outside the desert, passing through the desert
what is the definition of endoreic water sources
endoreic water sources occupy drainage basins within desert, staying within the desert
what is the definition of ephemeral water sources
rivers flow on the surface of the desert but only periodically after heavy rainstorms
perennial water
a maintained flow of water all year round
What are suspension and saltation
suspension- particles less than 0.2mm are carried within the air
saltation- this is where and sized particles bounce and hop along the surface. due to strong aeolian forces sand particles can be carried in the air
what are abrasion and deflation
abrasion - this is the sandpapering effect where material blasts against rock wearing it down
deflation - wind removed loose sand and clay particles leaving behind a bare desert pavement
explain the process of thermal fracture
rocks and and landforms within the desert experience rapid heating and cooling or rocks. this extreme diurnal range causes rocks to expand at night and contract during day, this causes rock to wear and brake away
what is desertification
the persistent degradation of dryland ecosystems by human activities and climate change
explain how over cultivation causes desertification
over cultivation - due to increased land use for growing crops and farming land does not have time to recover leaving it bare and exposed to desertification
key facts
Ethiopia’s population has increased by 300% since 1950
over 650,000 km of land have been taken over by the Sahel region since 1940s
areas at risk of desertification lose 23.16% of annual GDP
severe droughts in the Sahel and improper land use have led to 250,000 deaths along with 3.5 million cattle in the 1970’s
what are the different types of flooding
sheet flooding - shallow level of flooding which carries loose material across a surface
channel flooding - the flooding is channelized and steep valleys travelling at a faster pace. they can move significant loads of sediment and have huge potential for erosion
